Garson Kanin began his show business career as a jazz musician, burlesque comedian, and actor. He graduated from the American Academy of Dramatic Arts in New York City and made his Broadway debut in Little Ol' Boy (1933). In 1935, Kanin was cast in a George Abbott play and soon became Abbott's assistant. Kanin made his Broadway debut as a director in 1936, at the age of twenty-four, with Hitch Your Wagon.

In 1945, Kanin directed Spencer Tracy in Tracy's first play in 15 years. Tracy had been through a dark patch personally—culminating with a stay in hospital—and Katharine Hepburn felt that a play would help restore his focus.[1] Tracy told a journalist in April, "I'm coming back to Broadway to see if I can still act." The play was The Rugged Path by Robert E. Sherwood, which first previewed in Providence, Rhode Island on September 28, to a sold-out crowd and tepid response.[2]

The Rugged Path was a difficult production, with Kanin later writing, "In the ten days prior to the New York opening all the important relationships had deteriorated. Spencer was tense and unbending, could not, or would not, take direction".[3] Tracy considered leaving the show before it even opened on Broadway,[4] and lasted there just six weeks before announcing his intention to close the show.[5] It closed on January 19, 1946, after 81 performances.[6] Tracy later explained to a friend: "I couldn't say those goddamn lines over and over and over again every night ... At least every day is a new day for me in films ... But this thing—every day, every day, over and over again."[7]

Kanin's Hollywood career was interrupted by the draft. He served in the United States Army from 1941 to 1945. During this time Kanin, with Carol Reed, co-directed General Dwight D. Eisenhower's official record of the Allied Invasion, the Academy-award-winning documentary The True Glory (1945). During this time, he began writing what would become his greatest play, Born Yesterday.

His most famous quote, from his hit play "Born Yesterday," is on a New York City Public Library plaque on a 41st Street sidewalk: "I want everyone to be smart. As smart as they can be. A world of ignorant people is too dangerous to live in."